Pain is a major problem for individuals and for society. The scientific search for pain signals has been going for decades. Chronic pain is a common and often serious condition, and it reduces the ability of a person to function effectively and enjoy life. In extreme cases, living becomes unbearable for the patient. Chronic pain has been linked to stress, traumatic experiences, genetics, and environmental factors. The present lack of objective, affordable, and safe methods of testing for pain makes it difficult for many people to prove that their pain is in fact real. Without proof, they face many additional problems. For example, their pain may be doubted by employers, doctors, families, and insurance companies. The lack of objective tests for pain is a problem not only for the sufferer, but also for society in general. For example, adjudicators of accident cases lack tools to decide who to believe—when employees seek disability leave, employers have trouble knowing if they should be compassionate and flexible or firm, and doctors don't know if a request for analgesics is reasonable. However, even transient or short-term pain can provide significant challenges to a patient's quality of life.
There is a need for improved subjective and objective methods of measuring and classifying mechanical pain (i.e. pain induced by exertion of force upon the body). There is also a need for devices that can measure, test for, and research losses in the touch system of the body (the “somatosensory system”). (“Somatosensory” is used herein to indicate sensory activity having its origin elsewhere than in the special sense organs [e.g., eyes and ears] and conveying information about the state of the body proper and its immediate environment—examples of somatosensation include light touch sense, mechanical pressure sense of the skin and deep tissues, dynamic/moving touch sense, and vibration sense.) These losses are found in many common medical conditions, including various diseases called neuropathies.
Touch sensation includes several factors including: superficial mechanical touch (e.g., a cotton ball passed lightly over the skin), deep mechanical touch (e.g., a subject is pressed through superficial soft tissues hard enough to push on/near bone); the ability to feel any movement over the skin, the ability to identify letters and shapes traced upon the skin, and the ability to sense vibration. Numerous diseases are known to affect the touch system. Loss of sensation may be tested by looking for touch thresholds such as the minimum pressure needed so that the subject can feel that he or she is being touched at all.
Standardization of the applied force stimulus is particularly important for certain techniques of the objective testing of pain and touch. Without reproducible force-applied stimuli, it is very difficult to do accurate scientific research into pain and its associated disorders, or to diagnose or treat patients having certain types of pain and touch dysfunctions.
Existing automated somatosensory mechanical stimulators include algometers (which test for mechanical pain), which are inaccurate and fail to deliver a sufficiently standardizable applied-force stimulus and also cannot press as lightly as is desirable to test for the loss of touch.